How to write a bare-metal hello world program for PowerPC

Question

I need to write a program on bare-metal PowerPC system. As a newbie to bare-metal programming without OS/bootloarder, I decide to write a hello world program to start. I googled some post about this, and found out something about ARM like Beagleboard bare metal programming or Hello world, bare metal Beagleboard.

I don't very clear if they are suitable for porting to PowerPC platform. I cannot find PowerPC's hello world example for beginner. Anyone have experience of bare-metal development for PowerPC, without bootloader or OS?

Thanks.

Creamcolored

Answer 1

Random notes/links I collected for trying to get a bare metal PPC system to boot in Qemu There are plenty of examples all around for doing embedded, bare-metal programming on ARM platforms, but the PowerPC examples seem to be sparse.

Some ARM links:

http://opensourceforu.com/2011/07/qemu-for-embedded-systems-development-part-2/ https://balau82.wordpress.com/2010/02/28/hello-world-for-bare-metal-arm-using-qemu/

Building GNU GCC cross compiler

1) Packages Needed

binutils https://ftp.gnu.org/gnu/binutils/

GCC https://ftp.gnu.org/gnu/gcc/gcc-4.1.1/

newlib ftp://sourceware.org/pub/newlib/index.html

GDB http://www.gnu.org/software/gdb/gdb.html

2) Set environment variables

$ export TARGET=powerpc-eabi
$ export PREFIX=/usr/local/$TARGET
$ export PATH=$PATH:$PREFIX/bin

3) Build binutils

$ tar xjfv binutils-2.17.tar.bz2
$ mkdir build-binutils
$ cd build-binutils
$ ../binutils-2.17/configure --target=$TARGET --prefix=$PREFIX
$ make all
$ make install

4) Build bootstrap GCC

$ tar xjfv gcc-4.1.1.tar.bz2
$ mkdir build-gcc
$ cd build-gcc
$ ../gcc-4.1.1/configure --target=$TARGET --prefix=$PREFIX --without-headers --with-newlib  --with-gnu-as --with-gnu-ld
$ make all-gcc
$ make install-gcc

5) Build newlib

$ tar xzfv newlib-1.14.0.tar.gz 
$ mkdir build-newlib
$ cd build-newlib
$ ../newlib-1.14.0/configure --target=$TARGET --prefix=$PREFIX
$ make all
$ make install

6) Build GCC again with newlib

$ cd build-gcc
$ ../gcc-4.1.1/configure --target=$TARGET --prefix=$PREFIX --with-newlib --with-gnu-as --with-gnu-ld --disable-shared --disable-libssp
$ make all
$ make install

7) Build GDB

$ tar xjfv gdb-6.3.tar.bz2  
$ mkdir build-gdb
$ cd build-gdb
$ ../gdb-6.3/configure --target=$TARGET --prefix=$PREFIX --enable-sim-powerpc --enable-sim-stdio
$ make all
$ make install

Example bare metal hello world!!! https://github.com/ara4711/ppc_hw

• In makefile change, PREFIX=$(PROC)-$(TYPE)- to PREFIX=/usr/local/powerpc-eabi/bin/$(PROC)-$(TYPE)-

• In makefile give path of qemu-system-ppc to QEMU variable.

• Command make will generate the test.bin.

• Command make run will load the binary and the print “Test Hello
  world!“ is displayed on the console

• Command make debug to debug test program.

• Press Ctrl+a and x to terminate QEMU

QEMU implements a gdb connector using a TCP connection. To do so, run make debug

this command freezes the system before executing any guest code and waits for a connection on the TCP port 1234. From another terminal, run powerpc-eabi-gdb and enter the commands:

target remote localhost:1234
file test.elf

This connects to the QEMU system and loads the debugging symbols of the test program, whose binary image is already loaded in the system memory. From there, it is possible to run the program with the continue command, single-step the program and debug it in general. The exit command in gdb closes both the debugger and the emulator.

Fleming

Answer 2

First of all, which CPU is this? Secondly, the CPU is not everything.

If you have no starting point, you can study up the BIOS of the architecture you want to write this code for. Then you can write a boot sector which gives you the output you want. Check this page for some examples: Rough guide to assembly

Giveandtake

CPU is PPC4xx. I will run program on QEMU, a VM. I find a hello world program for ARM from opensourceforu.com/2011/07/… . If I want to port it to PowerPC, how should I do? – Creamcolored

It looks like that code is utilizing custom libraries. In that case you can install the arm toolchain into your emulator and compile your code on the emulator itself. The alternative is to obtain a cross compiler for PowerPC and after compiling it, you can upload it into the emulator. – Giveandtake

@Creamcolored What is exactly the platform you use under QEMU? I think you should first look at how to start a bootloader like u-boot or OpenFirmware. This is a mandatory step to have the low-level part initialized (caches, MMU, serial port, ...) and then write a standalone helloworld. – Bui

@Bui My choice is board xilinx virtex-ml507. I add my new device by mmio. I am reviewing the code of U-Boot. But I still hope to get a brief hello world example. – Creamcolored

Answer 3

Based on the @Pratik Parvati's answer, I have updated instructions for 2023 and more recent tool-chains.

• I had to install native qemu-system-ppc libmpc-dev libmpfr-dev libgmp10 packages on my system to compile/run everything.
• I used the latest version of everything: binutils-2.40.tar.xz gcc-13.1.0.tar.xz gdb-13.2.tar.xz newlib-4.3.0.20230120.tar.gz from https://ftp.gnu.org/gnu/binutils/ https://ftp.gnu.org/gnu/gcc/ https://ftp.gnu.org/gnu/gdb/ https://sourceware.org/newlib/. Plus git clone https://github.com/ara4711/ppc_hw.git

I executed the following commands:

• mkdir build-gcc build-binutils build-newlib build-gdb
• binutils: ( cd build-binutils; export TARGET=powerpc-eabi; export PREFIX=/usr/local/$TARGET; export PATH=$PREFIX/bin:$PATH; ../binutils-2.40/configure --target=$TARGET --prefix=$PREFIX && make -j4 all && make install)
• Based on some other guidance (maybe unneeded) I put a newlib symlink in gcc: ln -s newlib-4.3.0.20230120 gcc-13.1.0/.
• gcc: ( cd build-gcc; export TARGET=powerpc-eabi; export PREFIX=/usr/local/$TARGET; export PATH=$PREFIX/bin:$PATH; ../gcc-13.1.0/configure --enable-languages=c --disable-multilib --target=$TARGET --prefix=$PREFIX --without-headers --with-newlib && make -j4 all-gcc && make install-gcc)
• newlib: (cd build-newlib; export TARGET=powerpc-eabi; export PREFIX=/usr/local/$TARGET; export PATH=$PREFIX/bin:$PATH; ../newlib-4.3.0.20230120/configure --target=$TARGET --prefix=$PREFIX && make -j4 all && make install)
• gdb: (cd build-gdb; export TARGET=powerpc-eabi; export PREFIX=/usr/local/$TARGET; export PATH=$PREFIX/bin:$PATH; ../gdb-13.2/configure --target=$TARGET --prefix=$PREFIX && make -j4 all && make install)
• ppc_hw: (cd ppc_hw; sed -i -e 's:~.*/::' -e 's/-gstabs\+//' makefile; export TARGET=powerpc-eabi; export PREFIX=/usr/local/$TARGET; export PATH=$PREFIX/bin:$PATH; ( make all || make all ) && ((sleep 10; skill qemu-system-ppc) & make run))

I have not attempted to use gdb yet.

I was unable to use newlib successfully. When I attempted to use snprintf, after defining noop random system calls the linker forced me, I got an illegal instruction in QEMU. Instead I switched to https://github.com/PetteriAimonen/Baselibc and after minor hacking was able to get that to work, at least at the snprintf level.

Discursive